The invention relates to a multifunctional unit, particularly a starter unit for use in change-speed gearboxes, and particularly automatic and automated change-speed gearboxes, and it further relates to a change-speed gearbox, in particular an automated change-speed gearbox and to a vehicle with a change-speed gearbox.
Gearboxes for use in vehicles, in particular commercial vehicles, in the form of change-speed gearboxes or automated change-speed gearboxes are known in a large number of different embodiments. The starting process is usually realized using a coupling device in the form of a friction clutch or a hydrodynamic converter. However, use of a friction clutch as a starter element caused problems during operation, characterized by increased slip over a longer time period. This applies especially to the starting process. Due to the enormous thermal loading, the coupling device is then subjected to increased wear. In order to keep this wear as low as possible, appropriate demands are placed on the friction lining used. Furthermore, the appearance of wear causes low service life for the starter element.
The disadvantage of using starter elements in the form of hydrodynamic converters consists of the high costs for the hydrodynamic part and the requirement to provide a clutch mechanism.
An embodiment of a physical gearbox unit with a starter element in the form of a turbocoupling is known from German publication DE 196 50 339 A1. At least two operating states are obtainable, namely a first operating state for transmission of power in at least one gear stage and a second operating state for braking. Both functions are realized using a hydrodynamic coupling. This comprises a pump wheel and a turbine wheel, which together form a toroidal working area. The function of a hydrodynamic retarder is obtained by the function of the stator blade wheel, either by fixing with respect to a stationary gearbox component, to the pump wheel and the function of the rotor blade wheel to the turbine wheel, or the assignment of the function of the stator blade wheel to the turbine wheel by fixing the turbine wheel with respect to the stationary gearbox components and the function of the rotor blade wheel to the pump wheel. In both cases, the blade wheel, which takes over the function of the rotor blade wheel, is coupled to the gearbox output shaft by means of the mechanical gearbox component. At the same time, the turbocoupling is connected to the drive shaft or the mechanical gearbox component of the physical gearbox unit such that, in order to realize the first operating state, the turbine wheel can be connected to the mechanical gearbox component and the pump wheel to the gearbox input shaft, while, to realize the second operating mode, i.e. braking, one of the two blade wheels is fixed. For this purpose, means for fixing and decoupling from the drive train are assigned to the hydrodynamic coupling, in particular to a blade wheel. This embodiment allows particularly compact physical gearbox unit to be formed, as a separate braking element can be dispensed with. However, it has the disadvantage for automatic change-speed gearboxes, in which the engine or turbine experiences a considerable change of speed during the gear-shifting process, during which the speed of the turbine wheel has to be synchronized. However, when used in an automated change-speed gearboxes, a separate clutch mechanism must be provided in order to guarantee reliable interruption of the power flow during gear-shifting processes.